Banknote processing technology plays a more and more important role in an extensive application of financial self-service equipment, such as ATM machine. Banknote processing technology is no longer limited to basic currency denomination recognition and authentication. In particular, since cash recycling technology has been applied, the detection of circulation ability of banknote becomes more and more important. On one hand, a banknote having a poor condition is easy to be damaged and is not suitable to be circulated in the market. On the other hand, a banknote having a poor condition readily causes failure of self-service equipment, such as banknote overlapping, banknote connection and banknote jam. In the detection of circulation ability of banknote, a detection for banknote crack is recognized as a hard problem in the industry. A banknote crack is usually one or multiple cracks on the banknote face due to tearing, folding, or cutting. If there is a banknote with cracks in self-service equipment, such as an ATM machine, in a process of trading, the banknote likely causes banknote jam when the banknote is conveyed in a channel of the self-service equipment. Once the failure of banknote jam occurs, the service of the equipment has to be stopped until the banknote is cleared by a professional person, which has a serious impact on transactions for the customer. Therefore, it is critical to effectively detect whether there is a crack on the banknote and determine whether the crack is serious enough to cause the failure of banknote jam. Thus, it is necessary to solve the problem of banknote crack detection in the industry.